The objective of this work is to develop the chemistry of Tc in its lower oxidation states in order to provide starting materials with high affinities for nitrogen sites on biologically important compounds. This should lead to the development of rapid synthetic methods for Tc radiopharmaceuticals to be used in cancer diagnosis. These include: 1) Tc complexes with the ability to undergo in vivo reduction and so be preferentially activated by the reducing environment of many types of cancer tissue toward binding and fixation in such tissues, and 2) Complexes with nitrogenous biomolecules, such as amino acids or nucleotides, which will cause the radionuclide to concentrate in neoplastic tissues. Localization of 99m Tc in cancerous lesions by either of these methods should facilitate the detection of neoplasms by safe, non-invasive radioscintigraphic techniques.